Auger bits have been used to drill holes in utility poles made of wood for a number of years. These auger bits usually have a feed screw near their tip that helps propel the bit through a pole, at least one cutting edge located below the feed screw near the outer circumference of the main shaft of the auger bit that enables the auger bit to cut through the wood, a main shaft with a generally cylindrical shape that has at least one flute that extends from the cutting edge and allows chips formed by the auger bit as it bores into a pole to be removed from the cutting site, and a shank portion that has a diameter that is less than the main shaft that extends from the bottom of the main shaft of the auger bit.
The shank portion typically has three flats milled about its periphery which allow it to be easily held in a chuck of a powered drill or impact wrench which can be used by the user to cause the auger bit as a whole to rotate. As the auger bit rotates, the threads of the feed screw help to propel the auger bit through the pole, making it easier for the user to complete the boring operation. At the same time, the cutting edges remove material as the auger bit rotates and send this material along the flute of the bit, allowing deep holes to be bored.
When being used in the field, it is common for an auger bit to hit nails that are within the wooden pole. This can cause damage to the feed screw and cutting edges, impairing the function of the auger bit. For example, the threads of the feed screw could be deformed which prevents the auger bit from self feeding through the pole as it rotates, requiring the user to push and work harder to bore a hole. Likewise, the cutting edges can become chipped or dulled so that they do not efficiently remove wood chips making boring slow. Consequently, a number of techniques have been developed to remedy these problems.
For example, U.S. Pat. No. 1,389,578 discloses an auger bit that has a replaceable insert that has the feed screw and cutting edges incorporated therein. The replaceable insert can be attached to the shaft of the auger bit using a single screw. This design, however, has two disadvantages. First, the manufacturing the insert is difficult and costly because of the configuration of the replaceable insert because it includes both the feed screw and cutting edges. Second, both the feed screw and the cutting edges are replaced regardless of what features have been damaged on the auger bit, forcing the user to buy and use a replacement insert that is often more costly than necessary.
U.S. Pat. No. 5,820,319 discloses an auger bit that has replaceable feed screw that is attached to the shaft by means of a single screw. This technique, however, does not provide for any way to replace worn cutting edges. Therefore, this auger bit does not allow the user to handle situations when the cutting edge has become dull. Conversely, U.S. Pat. No. 6,024,520 discloses replacing cutting edges using a screw to attach the replaceable cutting insert to the shaft, but provides no means to replace the feed screw. Thus, neither U.S. Pat. No. 5,820,319 nor U.S. Pat. No. 6,024,520 provides a suitable way to replace both feed screw and cutting inserts, giving the user the needed flexibility to address problems in the field.
Finally, U.S. Pat. Nos. 4,625,593 and 6,361,255 disclose replaceable feed screws and cutting inserts, but neither show how they can be attached in a quick and effective manner. U.S. Pat. No. 4,625,593 discloses that the insert is brazed onto the shaft making replacement difficult, while U.S. Pat. No. 6,361,255 fails to specify the exact means by which the feed screw and cutting insert are attached in a replaceable manner to the shaft of the auger bit.
Accordingly, there exists a need for an auger bit that has a replaceable feed screw and a replaceable cutting insert that can be attached in a quick manner, and that allows the user to select which feature needs to be replaced in a cost effective way.